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Puberty Defining - Anatomy & Physiology (view source)
Revision as of 13:33, 5 July 2012
, 13:33, 5 July 2012no edit summary
== Introduction ==
Generally, puberty can be defined in both sexes as the ability to accomplish reproduction. The fundamental requirement for the onset of puberty is the secretion of GnRH at the appropriate frequency and quantity to stimulate gonatotrophin release by the [[Pituitary_Gland_- Anatomy & Physiology#Anterior_Pituitary_Gland|anterior pituitary gland]]. Gonadotrophins promote:
Generally, puberty can be defined in both sexes as the ability to accomplish reproduction. The fundamental requirement for the onset of puberty is the secretion of GnRH at the appropriate frequency and quantity to stimulate gonatotrophin release by the anterior pituitary gland. Gonadotrophins promote:
* Gametogenesis
* Gametogenesis
* Steroidogenesis
* Steroidogenesis
* Development of reproductive organs
* Development of reproductive organs
The degree of function of neurons in the hypothalamus that secrete GnRH increases as puberty begins. The function of these neurons may be influenced by:
The degree of function of neurons in the [[Hypothalamus_- Anatomy & Physiology|hypothalamus]] that secrete GnRH increases as puberty begins. The function of these neurons may be influenced by:
* Plane of nutrition
* Plane of nutrition
* Exposure to certain environmental or social cues
* Exposure to certain environmental or social cues
* Genetics
* Genetics
= Male=
== Male==
=== Age when Behavioural Traits are Expressed ===
* Generally acquire reproductive behavioural traits such as [[Copulatory Behaviour - Anatomy & Physiology#Mounting|mounting]] and [[Pre-copulatory Behaviour - Anatomy & Physiology#Erection|erection]] a long time before they acquire the ability to [[Copulatory Behaviour - Anatomy & Physiology#Ejaculation|ejaculate]] and produce spermatozoa.
* Behavioural traits are easy to determine, as [[Copulatory Behaviour - Anatomy & Physiology#Mounting|mounting behaviour]] and [[Pre-copulatory Behaviour - Anatomy & Physiology#Erection|erection]] can be easily observed.
=== Age at First Ejaculation ===
* [[Copulatory Behaviour - Anatomy & Physiology#Ejaculation|Ejaculation]] is a complex process,requiring coordinated development of nerves, specific muscles and secretion of seminal fluids from the accessory sex glands.
* When development of all of these components occurs, [[Copulatory Behaviour - Anatomy & Physiology#Ejaculation|ejaculation]] can take place.
* Generally the ability to [[Copulatory Behaviour - Anatomy & Physiology#Ejaculation|ejaculate]] preceeds the ability to produce sufficient spermatozoa to achieve [[Fertilisation - Anatomy & Physiology|fertilization]].
=== Age when Spermatozoa First Appear in the Ejaculate ===
* Males acquire the ability to produce seminal fluid and [[Copulatory Behaviour - Anatomy & Physiology#Ejaculation|ejaculate]] before spermatozoa are available to be [[Copulatory Behaviour - Anatomy & Physiology#Ejaculation|ejaculated]].
* To determine when spermatozoa first appear, the ejaculate must be collected at least once per week.
** Easy to collect using an artificial vagina from the the boar, bull, dog, ram or stallion.
* After behavioural characteristics have developed and the male is willing to [[Copulatory Behaviour - Anatomy & Physiology#Mounting|mount]] a receptive female/surrogate, frequent seminal collection is possible.
** Enables determination of the age at which spermatozoa first appear in the ejaculate.
=== Age when Spermatozoa First Appear in the Urine ===
* Most spermatozoa produced are lost in the urine during periods of sexual abstinence.
* The presence of sperm in the urine indicates that [[Spermatogenesis_and_Spermiation_- Anatomy & Physiology|spermatogenesis]] is occuring.
* Frequent urine collection is difficult in large domestic species and requires special equipment, so this method of determining pubertal onset has limitations.
=== Age when the Ejaculate Contains a Threshold Number of Spermatozoa ===
* Even if the ejaculate contains spermatozoa, there may be insufficient numbers for optimum [[Fertilisation - Anatomy & Physiology|fertilization]].
* The presence of a threshold (minimum number) of spermatozoa is required. These thresholds vary between species.
* Reflect minimum seminal characteristics required to achieve pregnancy following [[Copulatory Behaviour - Anatomy & Physiology|copulation]].
* Practically, this is the most valid criterion for puberty in the male.
== Female ==
== Age when Behavioural Traits are Expressed ==
=== Age at First Oestrus ===
* The age that the female becomes sexually receptive and displays the first [[Oestrus Behaviour - Anatomy & Physiology|oestrus]].
* Easy to determine because females show outward behavioural signs of sexual receptivity, especially in the presence of a male.
* The first [[Ovulation - Anatomy & Physiology|ovulation]] is usually not accompanied by behavioural [[Oestrus Behaviour - Anatomy & Physiology|oestrus]] in heifers and ewes and is hence termed 'silent ovulation'. Thus, the age at first [[Oestrus Behaviour - Anatomy & Physiology|oestrus]] may not accurately reflect acquisition of puberty.
== Age when Spermatozoa First Appear in the Ejaculate ==
=== Age at First Ovulation ===
* The age at which [[Ovulation - Anatomy & Physiology|ovulation]] first occurs.
* Manual or visual validation is required. This can be accomplished by palpation of the [[Ovary - Anatomy & Physiology|ovary]] per [[Rectum_- Anatomy & Physiology|rectum]] in animals that are large enough to permit insertion of a hand/arm into the [[Rectum_- Anatomy & Physiology|rectum]] (cow and camelids).
* Ultrasound can be used most successfully in the mare to determine ovarian status.
* When [[Ovulation - Anatomy & Physiology|ovulation]] has occured, a soft depression on the surface of the [[Ovary - Anatomy & Physiology|ovary]] can be palpated.
* In smaller animals (sow, ewe, bitch, queen) surgical procedures are necessary to allow visualisation of the [[Ovary - Anatomy & Physiology|ovary]] in order to determine [[Ovulation - Anatomy & Physiology|ovulation]]. In addition laparoscopic observation can be used to determine when [[Ovulation - Anatomy & Physiology|ovulation]] occurs.
* All techniques require frequent observation of the [[Ovary - Anatomy & Physiology|ovary]], so although age at [[Ovulation - Anatomy & Physiology|ovulation]] is a good criterion for puberty, it is difficult to determine.
== Age when the Ejaculate Contains a Threshold Number of Spermatozoa ==
=== Age at which the Female can Support Pregnancy without Deleterious Effects ===
* Most practical definition in all domestic animals.
* Acquisition of a threshold body size is important in controlling onset of puberty.
* Energy requirements for follicular development and [[Ovulation - Anatomy & Physiology|ovulation]] are small, however the metabolic cost of pregnancy and lactation are high so the female must reach a 'metabolic threshold' before puberty can occur.
[[Category:Puberty]]
[[Category:Bullet Points]]